Because many of the components and peripheral devices of both desktop and portable personal computers (PCs) consume a great deal of power even when they are not active, power management systems have been developed which cause each component or peripheral device to operate in the lowest power consumption mode with respect to present demands thereon. For example, U.S. Pat. No. 4,980,836 to Carter et al. discloses a power management system for a portable PC in which various peripheral devices are monitored for I/O activity. After a predetermined period of I/O inactivity, the PC is "powered down", i.e., the system clock is halted and power is removed from the hard disk drive, the floppy disk drive, the liquid crystal display (LCD), and miscellaneous system circuitry, thereby effecting more efficient use of remaining battery power.
Since Carter, improvements in the basic power management system have been introduced which include options such as blanking the liquid crystal display (LCD) or monitor screen after a predetermined period of I/O inactivity or turning off the hard disk drive motor after the hard disk drive has not been accessed for a predetermined period of time. Furthermore, there may be provided more than one reduced power consumption mode. For example, there may be a "stand by" mode in which certain components, such as the LCD and the hard disk drive motor, are caused to enter a reduced power consumption mode but the processing speed of the central processing unit (CPU) is not affected. In a "sleep" mode, nearly all of the functions of the PC are slowed or halted, including the CPU. From the standpoint of power consumption, the sleep mode is substantially equivalent to turning the PC off, except that no data is lost.
None of these power management systems fully responds to the fact that the various users of a single PC will most likely have differing work habits and preferences. For example, some users take frequent breaks throughout their work session but would prefer that the display not be blanked during each break, while others are prone to forget to turn off the PC following a work session. Some users want to maximize the battery life of a portable PC while others are concerned with avoiding the inconvenience of having the screen blank during data entry.
In addition to varying from user to user, the need for particular power management functions will vary from session to session, as different application programs will result in different work patterns. For example, a user will want to be able to examine a large spreadsheet or word processing entries without the screen being blanked at each momentary pause, but the same user will be indifferent to the screen being blank while the CPU is compiling a program or performing a scientific computation.
The above problems are partially solved by allowing the user to select the time-out parameters for particular program categories. Accordingly, by selecting the appropriate parameter values, a user is able to adapt the power management system to his or her own work habits with respect to a particular work session. For example, a longer time interval, such as ten or fifteen minutes, would be chosen for an application program which requires continuous I/O activity, such as word processing, than for one which performs scientific computations without a great deal of user input.
This solution is not entirely satisfactory, however, since a user will typically execute more than one application during a single work session, making it inconvenient for the user to change the timeout parameters each time he or she desires to use a different application. Further, novice users who are unaware of how to program the parameters will be forced to use the default parameters, which may not result in the most efficient use of power with respect to the particular work session. When time-out parameters are carelessly selected, the PC may often be caused to power-up or power-down at times which are inopportune or annoying to the user. As a result, the net power savings may be insignificant.
A power management solution is needed which both minimizes power consumption of the PC and which automatically adapts to the particular user's pattern of PC activity.